在PostgreSQL的基础上创建一个MongoDB的副本的教程

  CREATE TABLE some_collection (
   some_collection_id SERIAL NOT NULL PRIMARY KEY,
   data JSON
  );

  CREATE TABLE collection (
   collection_id SERIAL NOT NULL PRIMARY KEY,
   name VARCHAR
  );
 
  -- make sure the name is unique
  CREATE UNIQUE INDEX idx_collection_constraint ON collection (name);

 CREATE OR REPLACE FUNCTION create_collection(collection varchar) RETURNS
  boolean AS $$
   var plan1 = plv8.prepare('INSERT INTO collection (name) VALUES ($1)', [ 'varchar' ]);
   var plan2 = plv8.prepare('CREATE TABLE col_' + collection +
    ' (col_' + collection + '_id INT NOT NULL PRIMARY KEY, data JSON)');
   var plan3 = plv8.prepare('CREATE SEQUENCE seq_col_' + collection);
   
   var ret;
   
   try {
    plv8.subtransaction(function () {
     plan1.execute([ collection ]);
     plan2.execute([ ]);
     plan3.execute([ ]);
    
     ret = true;
    });
   } catch (err) {
    ret = false;
   }
   
   plan1.free();
   plan2.free();
   plan3.free();
   
   return ret;
  $$ LANGUAGE plv8 IMMUTABLE STRICT;

 SELECT create_collection('my_collection');

  CREATE OR REPLACE FUNCTION find_in_obj(data json, key varchar) RETURNS
  VARCHAR AS $$
   var obj = JSON.parse(data);
   var parts = key.split('.');
   
   var part = parts.shift();
   while (part && (obj = obj[part]) !== undefined) {
    part = parts.shift();
   }
   
   // this will either be the value, or undefined
   return obj;
  $$ LANGUAGE plv8 STRICT;

  SELECT data
   FROM col_my_collection
   WHERE find_in_obj(data, 'some.element') = 'something cool'

  CREATE OR REPLACE FUNCTION find_in_obj_int(data json, key varchar) RETURNS
  INT AS $$
   var obj = JSON.parse(data);
   var parts = key.split('.');
   
   var part = parts.shift();
   while (part && (obj = obj[part]) !== undefined) {
    part = parts.shift();
   }
   
   return Number(obj);
  $$ LANGUAGE plv8 STRICT;
   
  CREATE OR REPLACE FUNCTION find_in_obj_exists(data json, key varchar) RETURNS
  BOOLEAN AS $$
   var obj = JSON.parse(data);
   var parts = key.split('.');
   
   var part = parts.shift();
   while (part && (obj = obj[part]) !== undefined) {
    part = parts.shift();
   }
   
   return (obj === undefined ? 'f' : 't');
  $$ LANGUAGE plv8 STRICT;

  CREATE OR REPLACE FUNCTION save(collection varchar, data json) RETURNS
  BOOLEAN AS $$
   var obj = JSON.parse(data);
 
   var id = obj._id;
 
   // if there is no id, naively assume an insert
   if (id === undefined) {
    // get the next value from the sequence for the ID
    var seq = plv8.prepare("SELECT nextval('seq_col_" +
      collection + "') AS id");
    var rows = seq.execute([ ]);
    
    id = rows[0].id;
    obj._id = id;
 
    seq.free();
   
    var insert = plv8.prepare("INSERT INTO col_" + collection +
      " (col_" + collection + "_id, data) VALUES ($1, $2)",
      [ 'int', 'json']);
 
    insert.execute([ id, JSON.stringify(obj) ]);
    insert.free();
   } else {
    var update = plv8.prepare("UPDATE col_" + collection +
     " SET data = $1 WHERE col_" + collection + "_id = $2",
     [ 'json', 'int' ]);
 
    update.execute([ data, id ]);
   }
 
   return true;
  $$ LANGUAGE plv8 IMMUTABLE STRICT;

  {
   "name": "Jane Doe",
   "address": {
    "street": "123 Fake Street",
    "city": "Portland",
    "state": "OR"
   },
   "age": 33
  }
   
  {
   "name": "Sarah Smith",
   "address": {
    "street": "456 Real Ave",
    "city": "Seattle",
    "state": "WA"
   }
  }
   
  {
   "name": "James Jones",
   "address": {
    "street": "789 Infinity Way",
    "city": "Oakland",
    "state": "CA"
   },
   "age": 23
  }

  work=# SELECT create_collection('data');
   create_collection
  -------------------
   t
  (1 row)
   
  work=# SELECT save('data', '{ our object }');
   save
  ------
   t
  (1 row)

  {
   "$or": [
    {
     "address.state": "OR"
    },
    {
     "address.state": "WA"
    }
   ],
   "age": {
    "$gt": 30
   }
  }

  SELECT data
   FROM col_data
   WHERE find_in_obj_int(data, 'age') > 30
    AND (
       find_in_obj(data, 'address.state') = 'OR'
      OR
       find_in_obj(data, 'address.state') = 'WA'
      )

  work=# SELECT find('data', '{ "$or": [ { "address.state": "OR" }, { "address.state": "WA" } ], "age": { "$gt": 30 } }');